Compared to the Field Effect Thin Film Transistor (TFT) Liquid Crystal Display (LCD), the Active Matrix/Organic Light Emitting Diode (AMOLED) display as a novel display technique has many advantages in terms of view angle range, picture quality, efficiency, cost, and the like, and thus has a great potential for development in the field of a display production.
The active light-emitting diode display needs a higher driving current to achieve a perfect display effect since its light-emitting luminance is in a direct proportion to the driving current supplied to the OLED device, while the Low Temperature Poly-Silicon(LTPS) backboard technique is an optimum selection for the backboard technique of the AMOLED display since it can provide a higher mobility; nevertheless, the issue of the inherent threshold voltage drift in the low temperature poly-silicon technique causes the ununiformity in the driving current generated in the pixel circuit, and in turn raises a challenge of uniformity in the display luminance. Different driving voltages would generate different driving currents, resulting in the poor uniformity in the current, and thus the uniformity in the luminance is always poor.
The conventional 2T1C circuit as shown in FIG. 1 only comprises two TFTs, wherein T1 is a switch transistor and DTFT is a driving transistor for driving pixel; a scan line Scan turns on the switch transistor T1, and a data voltage Data charges a storage capacitor C; the switch transistor T1 is turned off during the period of light-emitting, and the voltage stored in the capacitor maintains the driving transistor DTFT to be turned on; the current flowing through the DTFT drives the OLED to emit light. In order to achieve a stable display, it is required that a stable current is supplied to the OLED. The voltage control circuit has advantages such as a simple structure, a fast speed for charging the capacitor, and the like, while the voltage control circuit has a disadvantage that it is difficult to perform a linear control on the driving current, since the uniformity in threshold voltage Vth of DTFT is very poor due to the low temperature poly-silicon manufacturing process, and at the same time the threshold voltage Vth also drifts; even if same technical parameters are used in the manufacture of the TFTs, there are large variations in the threshold voltages Vth of the different TFTs, thus giving rise to the issues of poor uniformity in the light-emitting luminance and luminance attenuation in the driving circuit for light-emitting.